MOTOR DRIVING SYSTEM

摘要

The drive circuit of a three-phase motor (1) generates a sine-wave PWM signal by using an induced voltage (11) and outputs a sine-wave current by driving upper and lower arms (2, 3, 4, 5, 6 and 7) according to the PWM signals. A filter (10) picks up the induced voltage (11) from an output voltage (9) and sends the voltage (11) to a sine-wave amplitude controlling section (12) and a speed measuring section (14). A microprocessor (15) measures the rotative speed of the motor (1) based on a speed signal from the speed measuring section (14) and controls the amplitude of the induced voltage (11) based on an amplitude controlling signal for acceleration and deceleration. Thereafter, PWM generating sections generate sine-wave PWM signals by using a triangular-wave carrier (13). In order to prevent through current from being generated at the output, preventive circuits (28, 29 and 30) comprising switches (35 and 36) and resistors (37 and 38) are provided. Through current is prevented also by offsetting the carrier (13). All the analog circuits of the integrated circuit are constituted of MOS circuits so as to simplify the process. By the system the power consumption of a brushless motor provided with no sensor is reduced to a half or less and, in addition, the electromagnetic noise of the motor is remarkably reduced. Moreover, since the analog circuits are constituted of MOS circuits, the manufacturing cost of the integrated circuit is reduced.